In prior practice, a first mold plate having a first mold cavity is disposed within a usually rectangular hole in a cavity plate, so that the surfaces of the mold plate and the cavity plate are substantially flush. Both the first mold plate and the cavity plate are secured to a support plate to constitute a first mold assembly. A second, complementary mold assembly, having a second mold cavity is then juxtaposed with the first described mold assembly to form a complete mold cavity, and material to be molded is injected into said cavity and allowed to set. The complementary mold assembly is then withdrawn and it becomes necessary to remove the molded article from the first mold cavity. This is normally done with ejector pins, which are movable in unison through said holes in the support plate, and are grouped in a pattern dictated by the contour of the first mold cavity.
Consequently, each time new mold cavity plates are inserted in a molding machine assembly, a new pattern for the ejector pins may be required. If so, the support plate must then be redrilled to establish such a pattern, conforming to the contour of the new mold cavity. Eventually, the support plate has such numerous holes that there is not enough metal left to accommodate new patterns, and the support plate must be replaced.
Further, the pins are normally headed pins, received in sockets in an ejector carriage plate, and are secured in said sockets by a retaining plate, apertured to pass the shanks of the headed pins, but not their head. Thus, to change a pattern of ejector pins, an ejector housing must be disassembled from the support plate, so that the ejector drive may be removed. Then the retainer plate must be removed so that the then existing pins may be withdrawn. Then the carriage plate must be redrilled to receive a new pattern of ejector pins, and, of course, accommodations must be made for the heads of the ejector pins. Eventually, of course, the carriage plate, like the support plate, must be replaced, because its metal will have been drilled and machined to the point that it cannot accommodate any further patterns of pins.